Studies will be directed toward the precise delineation of the physiological and biochemical mechanisms involved in the intestinal absorption and hepatic disposition of the biliary contrast materials (BCM). This is a continuation and extension of previous work on this subject. Like the earlier effort, the intent is to use the BCM as a tool to achieve a better understanding of basic hepatobiliary physiology, which will be relevant to the pathogenesis of cholelithiasis and cholestasis. The data will also permit more rational use of the BCM in clinical practice to improve oral cholecystography and intravenous cholangiography and lead to the development of safer, more efficient and more accurate contrast agents. The new phase of the project involves the use of different and more sophisticated analytic and experimental techniques (high pressure liquid chromatography, isolated perfused liver, cultured hepatocytes), to systematically study the following classes of compounds: triiodophenyl alkanoates, dimers of triiodobenzoic acid, phthalein dyes, fluorescein and conjugates of iopanoic acid. In addition and equally important, experiments will be performed to study systematically the uptake and excretion of various compounds (inorganic elements, pancreatic enzymes, amino acids, drugs and dyes) by the pancreas as 1) a basic project in pancreatic physiology of importance to understanding the pathogenesis of pancreatitis and pancreatic carcinoma and 2) a logical attempt to discover a contrast material for use in opacifying the pancreas with computerized tomography of the abdomen (CT scanning). The latter exploits the fact that the concentration of contrast material required with CT scanning is much less than is necessary with conventional radiography. This, coupled with the new finding that the pancreas has the ability to take up proteins from the blood and to excrete them into the pancreatic juice, makes the search for a material which will visualize the pancreas radiographically a feasible undertaking. Successful development of a pancreatic contrast material would permit the diagnosis of carcinoma of the pancreas at an earlier stage than ever before possible.